1. Field of the Invention
Aspects of the present invention relate to a lithium secondary battery, and more particularly, to a pouch-type lithium secondary battery that can prevent a metal layer of a case from being exposed.
2. Description of the Related Art
A pouch-type lithium secondary battery includes a flexible pouch-type case. The case includes upper and lower case portions, that are formed by folding a roughly rectangular film. A groove for receiving an electrode assembly is formed inside the lower case portion, through a pressing process, etc. After the electrode assembly is received in the groove, the upper and lower case portions are sealed, by a pressing and/or heating. To realize lightweight and small-sized electronic devices, the case is formed of a composite film that includes a metal layer and inner and outer resin layers provided on opposing sides of the metal layer. Accordingly, the case has excellent formability, and thus, its shape can be freely changed.
However, the metal layer is exposed at free ends (cut edges) of the case, when the case is sealed as described above. When the secondary battery is directly mounted in a hard case, or a battery box of an electronic device, with the exposed metal layer, a short may occur between the metal layer and a conductor of a protection circuit board, a conductor of the hard case or battery box, or an electrode of the battery.
In addition, the metal layer may be corroded by an electrochemical reaction, in the above cases. The corrosion of the metal layer may lead to swelling of the battery, which can reduce the performance and durability of the battery. In addition, when the end of the case is insulated, to prevent the above phenomenon, an additional insulation process is required, and thus, may increase production costs.